The basic idea of using an electric discharge to create singlet-delta oxygen to drive an energy transfer iodine laser dates back to 1974, but all attempts to produce such a device have failed for a variety of reasons (many related to an incomplete understanding of the complexity of the system as a whole).
Oxygen-iodine laser (OIL) systems operate on the electronic transition of the iodine atom at 1315 μm between the levels of I(2P1/2)→I(2P3/2) [hereafter denoted as I* (or excited iodine atoms) and I (or ground state iodine atoms), respectively]. The population inversion is produced by the near resonant energy transfer between the metastable excited singlet oxygen molecule, O2(a1Δ) [also denoted O2(a) hereafter], and the iodine atom ground state I. Conventionally, a two phase (gas-liquid) chemistry singlet oxygen generator (SOG) produces the O2(a) for a chemical oxygen-iodine laser (COIL). There are many system issues having to do with weight, safety and the ability to rapidly modulate the production of the O2(a) which have motivated investigations into methods to produce significant amounts of O2(a) using flowing electric discharges. Early attempts to implement electric discharges to generate O2(a) and transfer energy to iodine to make a laser failed to result in positive gain. Several investigations have also been conducted into the possibility of a continuous flow hybrid electrically powered oxygen-iodine laser with electric discharges to produce the O2(a). These studies have shown that flowing electric discharges through oxygen containing mixtures, typically diluted with a rare gas, can produce useful quantities of O2(a). Recent studies have demonstrated O2(a) yields greater than 15% using electric discharges and modeling results have indicated that such a system may produce a viable laser. More practical approaches were detailed in 2002 by Carroll et al in U.S. Pat. No. 6,501,780 the disclosure of which is incorporated herein by reference. Another possible approach is detailed in Hill's U.S. Pat. No. 6,826,222.